Detection of Nickel Sensitivity Has Increased

Abstract and Introduction

Background: Nickel allergy has been studied by contact dermatitis groups around the world, and the frequency of nickel sensitivity has been reported to be decreasing in some populations.
Objective: To review the prevalence of nickel allergy as observed by the North American Contact Dermatitis Group from 1992 to 2004.
Methods: The computer database of the North American Contact Dermatitis Group was used to examine the prevalence of nickel allergy over the study period and to analyze it by time, sex, and age.
Results: From 1992 to 2004, 25,626 patients were patch-tested. The percentage of women tested was fairly constant (61.4-66.3%). A steady increase in nickel sensitivity was seen from 1992 to 2004. Subgroup analysis did not identify a population with declining nickel allergy.
Conclusions: Nickel allergy continues to increase in younger and older men and women patch-tested in North America.

The North American Contact Dermatitis Group (NACDG) has tested patients suspected of having contact dermatitis and tracked the frequency with which various allergens produce positive results.^[1] Other similar groups from around the world have also reported this type of data. Prevalence data can provide cross-sectional estimates of the number of individuals affected at a given time. Data derived from patch-test patients, however, may lead to overestimation of the prevalence of allergy in the general population.

Nickel contact allergy has been widely studied.^{[2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]} Several studies have evaluated nickel allergy in the general population. One such study of 2,500 females in a Danish general population found nickel sensitivity in 14.5% of that population;^[3] an evaluation of 1,546 Danish female twins reported a prevalence of 9.6%.^[4] In two studies of nickel allergy in the general population, 0.8%^[5] to 0.9%^[6] of men were patch test positive whereas 8.0% and 9.0% of women were patch test positive (980 and 1,159 subjects, respectively).

Prevalence rates of nickel allergy are higher in patch-test populations. The percentage of patch-tested, patients that reacted to nickel ranged from 4.5% among 2,285 Japanese patients^[2] to 16% of 1,312 Scottish patients.^[7] When the data are analyzed by gender, nickel caused positive reactions in 1.8% of men in a European report^[8] and in 11% of 453 patients in a Nigerian analysis.^[9] For women, the reports ranged from 4.3% in Japan to 26% in Scotland. More recent reports on the rate of positive patch-test results include 17.7% of 5,557 patients from Singapore,^[10] 13.1% of 1,141 patients from Germany,^[11] 13.8% of 12,058 patients from the Czech Republic,^[12] and 17.3% of 10,511 patients from a group of nine European countries.^[13] A meta-analysis of 15 years of published data on the T.R.U.E. Test system of patch testing (Mekos Laboratories A/S, Hillerød, Denmark) found that 14.7% of 3,598 patch-tested patients were nickel sensitive.^[14]

Traditionally, the female predominance in nickel allergy has been linked to ear piercing, but that difference between the sexes has been changing. Many men adopted ear piercing in the later part of the last century, and a difference in nickel allergy has been identified in men with and without pierced ears. Five hundred twenty Swedish men in compulsory military service were patch-tested with nickel and cobalt (which commonly co-reacts with nickel and is found in many similar environmental sources). Among those with pierced ears, 7.9% had positive reactions; in those without pierced ears, 2.7% had positive results (p <.05).^[15] A study of the relationship of nickel sensitivity to ear piercing was conducted among the general population, and 14.8% of those with pierced ears were nickel sensitive, compared to 1.8% who were not pierced. In this cohort of 567 patients, 11.1% of women and 2.2% of men were allergic to nickel.^[16,17]

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